The present invention relates to an electric resistor designed for use as an electric conducting element in an electric circuit, said resistor presenting a given resistivity selectable from within a wide range and, more especially, being capable of varying its electrical resistance as a function of the pressure exerted on the resistor itself.
The conducting elements employed in electric circuits usually consisting of localized rheophores or resistors present a specific resistance depending on the size of the elements and the electrical characteristics of the materials from which they are made. For varying the electrical resistance of any one of the said conducting elements, the latter must be fitted with a variable resistor, which usually consists of a device comprising a very long resistor of which is used only a given portion presenting a given resistance between one end of the resistor and a slide travelling along the same. In addition to being highly complex, and therefore also expensive, a major drawback of variable resistors of the aforementioned type is that operation requires moving the slide along the resistor.
On certain types of known resistors, resistance is varied by altering the length of the resistor itself, subsequent to deformation of the parts to which the resistor is fitted (electrical straingauges). In this case, however, the resulting resistance changes must be amplified for worthwhile signals to be obtained. What is more, resistors of this type can only be supplied with very low current, which rules out any possibility of their being employed as effective conducting elements in electric circuits.